1. Field of the Invention
This invention relates in general to steel tubing and in particular to steel tubing made by a process of forming low sulfur content steel into a cylinder with the edges abutting, heating the edges and pressing them together so that they are joined and removing the inside bead of the weld with an inside cutter and the outside bead with an external cutter.
2. Description of Related Art
Tubing formed by drawing over a mandrel (DOM) requires the use of a draw bench, a mandrel, and an annealing process. In the process of producing DOM tubing, a tube is manufactured having specified interior and exterior diameters. This tube is then drawn over an internal bar which stretches the tube and gives it a specific ID. Typically, DOM tubing can hold an internal tolerance of approximately 0.005 inch. The tube is drawn over the mandrel so as to obtain the specific ID required and is then annealed so as to relieve stresses and obtain formability. The manufacture of steel tubing using DOM techniques is fairly expensive and the average sale price for electric resistance welded DOM tubing is fairly high. The DOM process is a batch process rather than a continuous process and the DOM process is energy, power and labor intensive.
See also the following U.S. Patents. U.S. Pat. Nos. 4,310,740, 4,354,090, 4,734,981, 4,796,798, 4,830,258, 4,905,885, 5,143,274, 5,148,960, 5,158,227.